Global navigation satellite systems (GNSS) utilize satellites to enable a receiver to determine position, velocity, and time with very high accuracy and precision using signals transmitted from the satellites. Such GNSS include the Global Positioning System (GPS), GLONASS, and Galileo. The signals transmitted from the satellites include one or more carrier signals at separate known frequencies, such as a first carrier (L1), a second carrier (L2), and an additional third carrier (L5) in the GPS. A code, such as a pseudo-random (PN) noise code modulated with information, may modulate a carrier of the signal, and may be unique to each satellite. Because the satellites have known orbital positions with respect to time, the signals can be used to estimate the relative position between an antenna of a receiver and each satellite, based on the propagation time of one or more signals received from four or more of the satellites. In particular, the receiver can synchronize a local replica of the carrier and code transmitted in a signal to estimate the relative position.
The most accurate GNSS systems are referred to as precise point positioning real-time kinematic (PPP-RTK) or global RTK. The algorithms used in PPP-RTK systems are a combination of the algorithms used in local RTK systems and PPP systems. Both local RTK systems and PPP systems can achieve high accuracy by determining carrier phase related ambiguities. In local RTK systems, a roving receiver receives real-time corrections from a nearby local reference station, such as through a radio link. Because the local reference station has a known precise location, it can help determine the precise location of the roving receiver. In PPP systems, a roving receiver receives corrections that are globally applicable, which eliminates the need for local reference stations. The corrections can include information regarding the position and clock error of satellites, so that the roving receiver can receive information regarding the precise location of the satellites to help determine the precise location of the receiver. PPP systems have a global network of reference stations that are used to develop the global corrections, which are then transmitted to the roving receiver.
PPP-RTK systems involve integer ambiguity resolution at the global network of reference stations and at the roving receiver. PPP-RTK systems are often used in applications such as precision farming, military navigation, and marine offshore positioning, due to its improved navigation accuracy and simplified infrastructure (i.e., eliminating the need for local reference stations). However, current PPP-RTK systems do not typically have real-time integer ambiguity resolution that is simultaneously stable, robust, and accurate, and with fast initialization times.
Accordingly, there is an opportunity for a satellite navigation receiver that addresses these concerns. More particularly, there is an opportunity for a satellite navigation receiver and associated methods that can provide improved integer ambiguity resolution and more accurate positioning information.